This invention relates to internal combustion engines and, more particularly, to presetting the engine and/or fuel injection components thereof to a predetermined condition prior to starting
The benefits of variable timing of intake and exhaust valves in reciprocating internal combustion engines are well known and include, among others, improved emissions and fuel consumption. Variable valve timing, in many cases, is achieved by replacing traditional cam-operated valve actuation systems with independent hydraulic or electrical actuators to control the opening and closing of the intake and exhaust valves. As a result, such engines are typically referred to as camless engines. The hydraulic or electrical actuators associated with each valve may be operated to open or close the valves at any desired point during the engine cycle to optimize engine performance in terms of emissions, brake specific fuel consumption, power and torque, etc. One skilled in the art will also recognize that variable valve timing is also beneficial when operating the engine with a compression release brake cycle to optimize the braking power available.
Examples of hydraulically operated camless engines are shown in U.S. Pat. No. 5,829,396 (Sturman) and U.S. Pat. No. 5,970,956 (Sturman), which are incorporated herein by reference. Another example of a hydraulically operated camless engine is also shown in commonly-owned U.S. Pat. No. Re. 35,303 (Miller et al.), which is also incorporated herein by reference.
In traditional, cam operated valve systems, a coil spring or the like is provided to bias the intake and exhaust valves to the closed position. However, hydraulic camless systems such as those shown in the Sturman ""396 and ""956 patents may be xe2x80x9cspringlessxe2x80x9d and rely on hydraulic pressure to both open the valves and also to return the valves to the closed position. Consequently, the possibility exists that the valves will drop from their closed position due to gravity during periods in which the engine is not operating and hydraulic pressure or cylinder pressure is not available to maintain the valves in the closed position. In such cases, it is possible that an undesirable collision may occur between the piston and the valves when starting the engine. This problem may also occur when using double acting electrical valve actuation if insufficient force is provided to latch or otherwise maintain the valves in their closed condition when the engine is not running.
In the case of hydraulic camless engines, hydraulically actuated fuel injection systems may be used to beneficially rely on a common high pressure hydraulic system. For example, the aforementioned Re. 35,303 patent utilizes hydraulic valve actuation and a hydraulically actuated fuel injector. Of course, hydraulically actuated fuel injectors may also be used in traditional, cam operated engine applications. In many traditional hydraulically actuated fuel injectors, high pressure fluid is used to drive a pumping plunger to pressurize and thereby inject fuel into the combustion chamber. The plunger is returned to its original position by a return spring, with the return stroke drawing a supply of fuel into the pumping chamber for the next injection event. However, hydraulically actuated fuel injectors such as those shown in U.S. Pat. No. 6,012,644 (Sturman), which is incorporated herein by reference, are xe2x80x9cspringlessxe2x80x9d and rely on hydraulic pressure to return the fuel injector plunger to its initial raised position, i.e. its position at the beginning of the full pumping stroke. As with the double acting hydraulic valve actuation systems mentioned above, the plunger is likely to drop due to gravity from raised position over time when the engine is not running. In addition, it is possible that the plunger may stop in other that its raised position when the engine is shut down. In either case, it is probable that the injector plunger will not be in its raised position when the engine is restarted, thus causing starting to be difficult or in some cases even precluding starting of the engine.
In some hydraulic valve actuation systems, pressure is maintained in the hydraulic circuit during period in which the engine is not operated by intermittently operating an auxiliary pump that supplies pressurized fluid to the system. An example of such a system, including a hydraulic valve actuation system in general, is illustrated in U.S. Pat. No. 5,410,994 (Schechter), which is incorporated herein by reference. While the system illustrated in the Schechter ""994 patent can provide a solution to the valve dropping concerns described above and the potential collision between piston and the engine valves during starting of the engine, the Schechter systems presents several additional challenges. For example, a system as illustrated in the Schechter ""994 patent requires the auxiliary pump to be powered between periods of engine operation perhaps several timesxe2x80x94which can cause a drain on the electrical system. Moreover, over long periods of non-operation, the system can become unpressurized due to a lack of electrical power, thereby permitting the aforementioned valve-piston collisions concerns to arise.
This invention is directed to overcoming one or more of foregoing problems.
In one aspect of this invention, a method of presetting an engine to a predetermined condition prior to starting is provided. The method comprises the steps of (a) providing an engine having unbiased components that have a tendency to move away from the predetermined conditions during period in which the engine is not operated; (b) prior to starting the engine, selectively supplying power to the unbiased components to position the components in the predetermined condition; and (c) thereafter, starting the engine.
In another aspect of this invention, an engine system for use with an internal combustion engine comprises a plurality of components forming a combustion system, at least some of the components have a predetermined condition for engine starting and being unbiased and further having a tendency to move away from the predetermined position during periods in which the engine is not operated. The engine system also comprises a starting system. The starting system comprises both a presetting system for selectively supplying power to the unbiased components to position the components is the predetermined condition and a cranking system operable independently of the presetting system for operating the engine until the engine achieves sustained combustion.
In yet another aspect of this invention, a method of starting an engine in a predetermined condition is disclosed. The method comprises the steps of (a) providing an engine having unbiased components that have a tendency to move away from the predetermined conditions during a period in which the engine is not operated; and (b) starting the engine. The starting step comprising the steps of (a) supplying power to the unbiased components to position the components in the predetermined condition; and (b) thereafter, powering the engine until the engine achieves sustained combustion.